As a future reference, it is not necessary to add your CSS files to your post, as they are able to be viewed on your site (and they will be removed by a moderator anyway).

The problem is that your <p> elements have 0 margin and 0 padding applied to them, which is why there is no separation between your paragraphs. How specific you want to be is up to you, but ultimately you need something like this:

p {
margin: 10px 0;
}

Adjust the actual pixel amount to your liking. You can also use padding in place of margin.